This invention relates generally to splice joints used to interconnect relatively short lengths of pole together end to end to form a longer pole. These poles, with a wire raiser, cable lifter or similar accessory attached to one end, are used by telephone and electric power utilities, contractors and CATV companies to perform maintenance on wires and transmitting equipment atop utility poles. This same type of pole with a pruning or saw head on one end is used by utilities and arborists to trim high limbs and branches from trees.
Since these poles frequently come into contact with wires carrying electric current, the pole itself is manufactured of a nonconductive material such as wood or fiberglass. In order to facilitate storage and transport of these poles from one place to another, they are manufactured in relatively short lengths--for example 3 feet or 6 feet--and then connected together when desired by a splice joint.
One type of splice used to connect pole sections together end to end is the slip-joint splice. This type of joint generally comprises interlocking male and female portions secured to opposite ends of each pole. When the male end portion is properly received in the female end portion, a through hole in a radial wall of one of the end portions is superimposed with a through hole in the radial wall of the other. An axially extending leaf, or flat, spring is secured to the outer surface of one of the poles and has an inwardly extending finger, or button, which is positioned under spring tension in the superimposed holes. In this manner, each pole is prevented from moving either away from, or twisting relative to, the other.
To disconnect the two poles, the finger is withdrawn from the aligned holes by moving the leaf spring away from the surface of the pole.
Because of the simple construction and light weight of the slip-joint splice, it is one of the most common means of joining pole sections together. Nevertheless, the slip-joint splice suffers from one substantial and long recognized disadvantage. Because the two pole sections are held together solely by the leaf spring finger extending through the superimposed holes, much of the tensile, compressive, and twisting force exerted on the splice is absorbed by the finger. Heavy duty use of the poles causes the finger to "wallow" within the superimposed holes, gradually enlarging them. When in this condition, excessive tensile or twisting force on the splice can force the finger from the holes, disconnecting the splice. For this reason, slip-joint splices have traditionally been used only where they are not subjected to excessive tensile or compressive loads. Other types of splices are customarily used under these heavy duty conditions and in general, are heavier, more expensive and difficult to connect and disconnect than the slip-joint splice.
So far as is known, no simple and inexpensive device has heretofore been devised which can lock a slip-joint splice against inadvertent disconnection, while being quickly and easily manipulated to permit disconnection when desired.